Newborns experiencing pain show the same patterns of brain activity as adults in discomfort, a new study has revealed.
Babies react in the same way to almost any stimulus: whether they are hungry, cold, tired or in discomfort, they can only cry.
As a result, some authorities have variously argued that infants can't therefore consciously perceive pain, because their nervous systems are insufficiently developed to process the relevant signals.
This has led to, in some cases, surgical procedures being carried out without any anaesthesia. A recent review also showed that infants in neonatal intensive care units undergo an average of 11 painful procedures each day, two thirds of them not covered by any analgesia.
Now Oxford scientist Rebeccah Slater has shown, by brain-scanning babies and adults as they experienced a consistent painful stimulus, that the same brain areas light up in both groups.
A total of twenty regions showed changes in their activity when a mature individual experienced a pain stimulus equivalent to being prodded with a pencil.
Eighteen of these same regions also lit up in the brains of ten newborn babies subjected to the same stimulus.
"This shows that the same circuits are activating in both in response to the pain," says Slater. "So we're making an assumption here that, because adults say they are in pain when they exhibit this pattern of brain activity, the newborns are too."
But what of the two brain areas that don't respond in the neonates?
"They're the orbitofrontal cortex, which is a part of the brain concerned with decision-making, and the amygdala, which is concerned with fear," explains Slater. "It's likely that these areas are not activating because young infants don't have the capacity for decision making about their experiences at their age, or the ability or necessity to be frightened."
Because babies cannot communicate their feelings like the adults in the study, it's impossible to say for certain that the infants are experiencing pain.
But, on the basis of the brain findings, the results, which have just been published by the journal eLife, suggest that infant analgesia needs to be taken at least as seriously as adult pain relief.
"The results might also be a starting point for studying the effectiveness of drugs to block pain in infants," points out Slater.
"We don't actually know if present pain killers work the same way in these individuals..."